This invention relates to an electromagnetic levitation device for causing relative levitation of first and second structure.
Such electromagnetic levitation devices have many uses in which one structure is inherently supported from another structure by an electromagnetic flux typically between an electromagnet and an associated armature. Whilst the electromagnet can be used to repel the armature, the present invention is particularly concerned with levitation devices in which the armature is attracted by the electromagnet. With such an arrangement the control of the current to the electromagnet is particularly critical when it is desired to retain the flux gap between the electromagnetic and its armature. Our co-pending British Patent Application No. 9604429.2 (GEC Case file P/60857/MRC) filed on Mar. 1, 1996 teaches how the electromagnetic force can be controlled by a control device which regulates the current to the electromagnet. The whole contents of that application are incorporated herein by reference.
In our co-pending British Patent Application No. 9604973.9 (GEC Case file P/60855/MRC) we have taught how a structure carrying machinery can be levitated within the hull of a vessel, using the electromagnetic attraction between an electromagnet and an armature, whilst keeping the flux gap open to inhibit the transmission of noise from the machinery to the hull, to inhibit the transmission of shock from the hull to the machinery, and to accommodate expansion and contraction of the hull by external hydraulic forces. The whole contents of that application are also incorporated herein by reference.
When two structures are inter-connected by an electromagnetic levitation device to achieve relative levitation using the attraction of an armature to an electromagnet, the flux gap can be controlled by the control device taught by our aforesaid co-pending patent application. However, if a significant shock is suddenly applied to one of the structures, this can close the flux gap with a consequence that the electromagnet and armature can suddenly impact with the danger of consequential damage.